326 Comparison of Psychological and Physiological Features Between Insomnia Patients with Short and Normal Objective Sleep Duration

Introduction Objective sleep duration has been suggested to be a novel biomarker in the phenotyping of insomnia (Vgontzas & Fernandez-Mendoza, 2013). It was hypothesized that insomnia phenotype with PSG-defined short sleep duration (< 6 hours) is associated with physiological hyperarousal, while the phenotype with normal sleep duration (≥ 6 hours), is associated with anxious-ruminative psychological profile and poor resources for coping with stress. The aim of this study was to assess whether these two insomnia phenotypes differ in terms of self-reported psychological and physiological features. Methods A total 45 (mean age=36.6, female=76%) insomnia patients underwent a polysomnographic evaluation, completed several self-rating scales (include ISI, BAI, BDI, FIRST, DBAS, and PSAS), and were split into two groups base on their objective sleep duration (cut-off 6 hours). Results When compared to the short sleep group using independent sample t-test, the normal sleep group showed a significant higher mean score on FIRST (t= -2.13; p< .05). The short sleep group showed non-significant trends to have higher mean scores on BDI and BAI. The scores on the other scales showed no significant differences between the two groups. The FIRST score correlated positively with the score of DBAS (r= 0.32; p< .05) and the total (r= 0.36; p< .05) and cognitive-subscale scores (r= 0.41; p< .01) on PSAS. The BAI score correlated positively with the score of the total (r= 0.53; p< .001) and somatic subscale (r= 0.59; p< .001) on PSAS. Conclusion These results support the hypotheses that the normal sleep phenotype tends to be more vulnerable to the impact of stress, especially on sleep, due to pre-sleep cognitive hyperarousal. Since the BAI scale contains more items regarding physiological symptoms of anxiety disorders, the tendency of higher BAI score in short sleep group may indicate that the short sleep phenotype has higher physiological arousal, which supports the phenotyping model proposed by Vgontzas and Fernandez-Mandoza. Support (if any)